STUDY ON SATURATION OF CR4+YAG PUMPED AT 1.06 MICROMETERS

we study the saturation of Cr4+ : YAG by measuring simultaneously the transmission T and the fluorescence energy E(Fluo). The adjustment of these results with the classic 4 levels model including excited state absorption (ESA) gives the following values of the ground state and th e ESA cross sections : sigma(a) = 2.3 10(-8) cm(2), sigma(ESA) = 3.2 1 0(-19) cm(2). However, this model does not explain the increase of E(F luo) that we noticed, We validate this measure by the conservation of energy and conclude that this model is not adapted, and that the ESA i s not the main factor responsible of the residual absorption at high f luences. A 3 levels model is proposed and a physical meaning of this m odel is sketched.